After you have implemented IWebPart make sure that you initialize the value to something that you want. See code below
private string description = "Loan details";
string IWebPart.Description
{
get
{
return description;
}
set
{
description = value;
}
}
private string subtitle = "";
[Personalizable]
[WebBrowsable]
[WebDisplayName("Subtitle")]
[WebDescription("Subtitle for this webpart.")]
string IWebPart.Subtitle
{
get
{
return subtitle;
}
}
private string title = "Loan";
string IWebPart.Title
{
get
{
return title;
}
set
{
title = value;
}
}
.
.
.
etc.